Pandit is an aging dog who has to be kept on a strict diet containing, among other things, 4.2 grams of protein and 8.8 grams of fat. two dog foods are available to pandit's owner: (i) food a has 6% protein and 20% fat, while (ii) food b has 6% protein and 7% fat. how many grams of food a should pandit's owner use in his diet?